docs: def experience(
        self, agent_indices, observ, action, reward, unused_done, unused_nextob):
      """Process the transition tuple of the current step.
  
      When training, add the current transition tuple to the memory and update
      the streaming statistics for observations and rewards. A summary string is
      returned if requested at this step.
  
      Args:
        agent_indices: Tensor containing current batch indices.
        observ: Batch tensor of observations.
        action: Batch tensor of actions.
        reward: Batch tensor of rewards.
        unused_done: Batch tensor of done flags.
        unused_nextob: Batch tensor of successor observations.
  
      Returns:
        Summary tensor.
      """
      with tf.name_scope('experience/'):
        return tf.cond(
            self._is_training,
            # pylint: disable=g-long-lambda
            lambda: self._define_experience(
                agent_indices, observ, action, reward), str)